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Re: Wood framed walls

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PRSE(--nospam--at)aol.com ( Bruce Resnick)wrote:
> 
> In my opinion:
> 
> Gypsum board is not an appropriate material for resisting racking shear.   

> Conclusions:  If you have "real" loads on your wall, put some plywood on
> the studs and do it right.
> 

In general I agree with Bruce, gwb is not worth much; its a wall
covering.  I have cyclicly tested many, many gwb 8' x 8' panels mostly
"non-conforming" construction and comparative code condition.  Its not
very strong (initially or after cycles) a design load of 30 to 50 lb/ft
is about right depending on nailing schedule.  However.....

The most important issue is that gwb completely gives up after about 1"
of cyclic deflection.  This is completely incompatible with plywood
which maintains strength to about 2.0" to 2.5" of cyclic deflection.  So
if you design a mixed material system and you get real cyclic
deflections beyond 1" all of your real gwb capacity will be gone setting
up the situation to overload the plywood.  

If you can design a 100% gwb system and assure yourself that the actual
earthquake induced story drifts (not some rw reduced displacement; a
real displacement accurately calced by response spectra or time history
analysis) are less than 1" >>> then go for it!  There have been cases
where 100% gwb systems have worked very well despite strong ground
motion.

If you are unwilling to use this approach then follow Bruce's advice

forget the gwb (zero value); use plywood.

Parting comment  >>> mixed systems can work and may be still allowed in
some areas but all plywood systems are the way to go for new
construction.

 regards

 Robert Kazanjy, PE    ***Disclaimer: I speak for myself not UC-Irvine
***
 Senior Development Engineer
 Civil & Environmental Engineering
 UC Irvine
 E4130 EG,  Zot: 2175
 rpkazanj(--nospam--at)uci.edu